Just about every blawg I read has a disclaimer on it.  The pattern is almost always the same, and reduces to the following:

• I am not your lawyer just because you’re reading this blog
• You are not my client just because you’re reading this blog
• This blog is not legal advice
• Don’t rely on anything in this blog if you’re looking for legal advice
• Talk to a lawyer if you need legal advice
• Unsolicited information sent to me is not protected by solicitor-client privilege

To my mind, posting a disclaimer on a blog is a little like handing a disclaimer to your dinner guests.  Of course blogs reach more people, but I still think the entire exercise is a little odd - it shouldn’t be necessary. Nonetheless, please tread carefully.